U.S. Provisional Application No. 61/384,947, filed Sep. 21, 2010, is incorporated herein by reference in its entirety.
Machine tools and machining centers, hereinafter sometimes jointly referred to by the term “machine tool”, including, but not limited to, milling machines and the like, include rotatable spindles configured for holding tools such as milling cutters, drills, reamers, and the like, for performing machining operations, such as but not limited to, milling, drilling, boring, and reaming. Such tools are typically removably held in the spindle by tool holders, which allow quickly changing the tools, for instance, by an automatic tool changing apparatus. Honing is a machining operation that can impart a much more precise size, shape, and finish to work piece bores, but many traditional honing tools require a feed mechanism or system for adjusting a feed position and/or feed force of honing elements, e.g., abrasive stones, of the tool, in process, as those elements are urged against the surface of a bore of a work piece for honing the bore. Known machine tools and machining centers lack the required feed system or mechanism, and thus the traditional in process adjustable feed honing tools have not been used on machine tools.
Several honing tools that have an in-process feed capability designed for use in machine tools lacking a feed system or mechanism, are known. Many machine tools have a through-the-spindle coolant delivery system, and it is known to use the pressure of this coolant to directly or indirectly force the honing elements or abrasive stones of the honing tool against the surface of the bore. Reference, Hyatt et al., U.S. Pat. No. 5,800,252, which discloses a honing tool designed for use in a machine tool having through-the-spindle coolant. By means of passages the coolant pressure is supplied directly to chambers behind the abrasive stones to provide direct force. However this type of tool allows each abrasive stone to feed independently, which has been found to lack an ability to reliably improve the roundness of a bore, which is often a goal of the honing process. In the traditional in-process adjustable feed honing tools, roundness is usually improved by having the honing elements or abrasive stones fed or moved by a single wedge element that keeps all of the honing elements or stones advancing or retracting in unison.
Reference also Becksvoort, et al., U.S. Pat. Nos. 6,739,949 B2, and 7,070,491 B2, which disclose an alternative to a traditional in-process adjustable feed honing tool, by having a wedge style feed element that is moved or fed by the pressure of coolant delivered through the machine tool spindle. However, neither these patents or Hyatt et al. discloses a manner of detecting when the honing operation has achieved the desired bore size. Typically, honing is done for a set period of time or some external means of in-process bore gauging is employed to determine when the desired bore size has been reached.
Reference also a 2010 technical paper, titled Integration of a Honing Tool into a Combination Machining Centre, by Paffrath and Biermann, which describes a “honing” tool for use in a machine tool. However, the disclosed tool is not a honing tool in the traditional sense. It consists of stones that are moved in the manner of a boring tool radially into the wall of a bore which requires significant rigidity and therefore is ill-suited to any bore except those that are very short relative to their diameter. In contrast, traditional honing tools are self supported in the bore by their honing elements or stones and possibly shoes that contact the bore in multiple angular locations, and the tools expand by changing diameter, which offers a significant advantage in the control of size and bore geometry.
None of the above referenced prior art discloses a manner of using traditional in-process adjustable feed honing tools on the spindle of a machine tool or machining center.
Thus, what is sought is a honing tool holder that provides a capability for automatically feeding the honing elements or stones when in the bore of a work piece, and for automatically stopping the feeding when a particular condition such as a bore size, is reached, to enable use of an in-process adjustable feed honing tool in a machine tool, machining center, or the like, lacking a feed mechanism or system.